1 .Field of the Invention
The invention relates to lasers and somewhat more particularly to a gas laser having a cylindrically-shaped discharge tube in which at least one end is terminated with a metal end cap which supports a mirror body in its central area and supports a metal pump stem positioned eccentric to the longitudinal axis of the tube.
2. Prior Art
Gas lasers having a cylindrically-shaped discharge tube having an end terminated with a metal end cap which supports a mirror body at a central area thereof and supports a metal pump stem in a position eccentric to the longitudinal axis of such tube are known; for example see German Offenlegungsschrift No. 26 04 740, German Auslegeschrift No. 25 06 707, U.S. Pat. No. 3,988,698, "Electronics", June 13, 1974 pages 91-95, or "Component Part Report", Vol. 14, 1976, pages 1-4, all of which are incorporated herein by reference.
These type of gas lasers are finding increased acceptance in the marketplace because of their simple and sturdy construction as well as their favorable price/output ratio. Practical experience has shown, however, that the presently available "coaxial" lasers of this type often still do not emit a light beam that is sufficiently directionally stable over extended periods of time, this despite their cylindrically-symmetrical construction. Thus, for example, the demands made for spatial constancy of the output radiation beam by a TV video-disk scanner (a typical application for these types of gas lasers) cannot be obtained without further ado. If one seeking to obtain spatial constancy of a laser beam from such lasers attempted to utilize usual techniques, perhaps by using select materials which have an extremely low thermal-expansion coefficient or by selecting materials which are thermally mated with one another or even by mechanically clamping the discharge tube into a structurally stable housing, then one would see that such conventional measures only insignificantly limit the characteristic migration of a laser beam during the warm-up period. Further, such beam stabilization means would detract from the decisive advantageous features of coaxial lasers, that is, the externally smooth or symmetrical construction and the low price thereof would be jeopardized by the inclusion of conventional beam stabilization means.